Recently i have been having 2 pop ups. One says the server for gadgets.live.com at DSL router, needs a username & password, and the other is wheather.service.msn.com at DSL router neeeds a username & password. I have had these before and they just went.

However, they ar now back, i have searched forums, i cant find much on it, apart from uninstall google taskbar, which i have done but i still get these annoying pop-ups.

Sounds like you are getting a prompt from your router to connect to these websites. Not a pop up as such (advert spam stuff) but a admin login appears.
I think it maybe that you have either got a browser hijack or hosts file been messed up and it's redirecting you to the router IP address.
Get Malware Bytes, run a scan and see if it finds out.